Two reports can show different totals because they answer different questions or include different records.
An invoice can have an invoice date, creation date, due date, and payment-related dates. A case has opened, closed, and status-change timing. An activity has scheduled and completion timing. Use the report's date labels rather than assuming every date range refers to creation.
Draft, open, sent, partially paid, paid, and void invoices are not interchangeable. Expense approval, client invoicing, and staff payment are separate states. Counts, currency amounts, hours, and mixed item quantities measure different things.
An incomplete current month should not be compared with a full prior month without noting the difference. A filtered report is not necessarily an organization-wide total.